Set 4 – Nuclear Coupling
- Page ID
- 79279
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- Consider the two hydrogen atoms HA and HB in the compound shown below.The X and Y groups are not hydrogen atoms and produce no magnetic fields.In particular, let’s focus on the effect that HB has on HA.We can think of HA “looking over” at HB and ask ourselves about the magnetic field produced by HB.
- What do you know from earlier in this unit about the magnetic field produced by HB?
- Is the flip of HB’s spin between the “with” and “against” states rapid or slow?
- What does the resonance for HA look like in the NMR spectrum?
- Which peak in the doublet corresponds to BHB “with” and which corresponds to BHB “against”?
- Can you think of a way to decouple a hydrogen atom like HB?
- What would the HB resonance look like?
- What would the resonance for HA look like in the compound shown below where there are two HB protons?Provide a rationale for your answer.
- Which peak of the triplet corresponds to the WW and which to the AA situation?
- What factors do you think influence the magnitude of the coupling constant?
- Predict the coupling constants that would occur between HA, HM and HX and the mono-substituted alkene shown below and draw the shape of each resonance.
- Consider the following compound in which JAB = 10 Hz, \(\delta\)HA = 1.3 ppm and \(\delta\)HB = 1.2 ppm. Draw the resulting spectrum if the spectrum is recorded on a 100 MHz and 400 MHz spectrometer.
